Thank you! I don't think it's Chara's hate. It's their guilt. The feel guilty for what monsters went through because they're human, even though they wish they weren't. And can I help you with the au? It could be like the caretaker au but with nice Chara!

I think that Chara was just a kid, Asriel said that Chara wasn't happy in the surface... put in her shoes (I like to think that was a girl, just my opinion) sometimes I hate humanity too...

Well... in my story (my regular AU "Under Adventure Tale") she didn't want to kill humanity 'cos she hated them, it was more about she overheard a conversation between Asgore and Gerson about how humans would kill them if they came to the surface... in this life is kill or be killed (I know, this is from Flowey XD)

Sorry, too late for the help, the whole story is in my head right now...

Something like...She never thought about diying, in this version she decides to kill the fallen humans by herself and save the souls for Asriel, for when they grow up, and thus Asriel would become the God of Hypedeath.

Imagine Chara at 12 years old saying "I think my chest is growing, what do you think, Asriel?" and he looks at her vaguely "maybe" and does not care because he's younger than she and still does not care about those things XDSince then, Toriel makes them sleep in separate rooms ...